<h1>Login</h1>
<p>
  <label for="username">用户名</label>
  <input type="text" id="username"
         [(ngModel)]="userInfo.username"
         name="username">
</p>
<p>
  <label for="password">密码</label>
  <input type="password" id="password"
         [(ngModel)]="userInfo.password"
         name="password">
</p>
<button (click)="login()">登录</button>
